Fig. 17-19, p. 399

1. Trade-Offs Solar Cells Advantages Disadvantages Fairly high net energy Need access to sun Work on cloudy days Low efficiency Quick installation Need electricity storage system or backup Easily expanded or moved No CO2 emissions High land use (solar-cell power plants) could disrupt desert areas Low environmental impact Last 20–40 years Low land use (if on roof or built into walls or windows) High costs (but should be competitive in 5–15 years) Reduces dependence on fossil fuels DC current must be converted to AC Fig. 17-19, p. 399

2. Trade-Offs Large-Scale Hydropower Advantages Disadvantages Moderate to high net energy High construction costs High environmental impact from flooding land to form a reservoir High efficiency (80%) Large untapped potential High CO2 emissions from biomass decay in shallow tropical reservoirs Low-cost electricity Long life span Floods natural areas behind dam No CO2 emissions during operation in temperate areas Converts land habitat to lake habitat May provide flood control below dam Danger of collapse Uproots people Provides water for year-round irrigation of cropland Decreases fish harvest below dam Decreases flow of natural fertilizer (silt) to land below dam Reservoir is useful for fishing and recreation Fig. 17-20, p. 400

3. Trade-Offs Wind Power Advantages Disadvantages Moderate to high net energy Steady winds needed High efficiency Backup systems needed when winds are low Moderate capital cost Low electricity cost (and falling) High land use for wind farm Very low environmental impact No CO2 emissions Visual pollution Quick construction Noise when located near populated areas Easily expanded Can be located at sea May interfere in flights of migratory birds and kill birds of prey Land below turbines can be used to grow crops or graze livestock Fig. 17-22, p. 403

4. Trade-Offs Solid Biomass Advantages Disadvantages Large potential supply in some areas Nonrenewable if harvested unsustainably Moderate to high environmental impact Moderate costs CO2 emissions if harvested and burned unsustainably No net CO2 increase if harvested and burned sustainably Low photosynthetic efficiency Plantation can be located on semiarid land not needed for crops Soil erosion, water pollution, and loss of wildlife habitat Plantations could compete with cropland Plantation can help restore degraded lands Often burned in inefficient and polluting open fires and stoves Can make use of agricultural, timber, and urban wastes Fig. 17-25, p. 405

5. Trade-Offs Geothermal Energy Advantages Disadvantages Very high efficiency Scarcity of suitable sites Moderate net energy at accessible sites Depleted if used too rapidly Lower CO2 emissions than fossil fuels CO2 emissions Moderate to high local air pollution Low cost at favorable sites Noise and odor (H2S) Low land use Low land disturbance Cost too high except at the most concentrated and accessible sources Moderate environmental impact Fig. 17-32, p. 410

6. Trade-Offs Conventional Oil Advantages Disadvantages Ample supply for 42–93 years Need to find substitutes within 50 years Low cost (with huge subsidies) Artificially low price encourages waste and discourages search for alternatives High net energy yield Easily transported within and between countries Air pollution when burned Low land use Technology is well developed Releases CO2 when burned Efficient distribution system Moderate water pollution Fig. 16-7, p. 363

7. Trade-Offs Conventional Natural Gas Advantages Disadvantages Ample supplies (125 years) Nonrenewable resource High net energy yield Releases CO2 when burned Low cost (with huge subsidies) Methane (a greenhouse gas) can leak from pipelines Less air pollution than other fossil fuels Lower CO2 emissions than other fossil fuels Difficult to transfer from one country to another Moderate environmental impact Shipped across ocean as highly explosive LNG Easily transported by pipeline Sometimes burned off and wasted at wells because of low price Low land use Good fuel for fuel cells and gas turbines Requires pipelines Fig. 16-11, p. 368

8. Trade-Offs Coal Advantages Disadvantages Ample supplies (225–900 years) Severe land disturbance, air pollution, and water pollution High net energy yield High land use (including mining) Low cost (with huge subsidies) Severe threat to human health Well-developed mining and combustion technology High CO2 emissions when burned Air pollution can be reduced with improved technology (but adds to cost) Releases radioactive particles and toxic mercury into air Fig. 16-14, p. 370

9. Trade-Offs Conventional Nuclear Fuel Cycle Advantages Disadvantages Large fuel supply Cannot compete economically without huge government subsidies Low environmental impact (without accidents) Low net energy yield High environmental impact (with major accidents) Emits 1/6 as much CO2 as coal Catastrophic accidents can happen (Chernobyl) Moderate land disruption and water pollution (without accidents) No widely acceptable solution for long-term storage of radioactive wastes and decommissioning worn-out plants Moderate land use Low risk of accidents because of multiple safety systems (except for 15 Chernobyl-type reactors) Subject to terrorist attacks Spreads knowledge and technology for building nuclear weapons Fig. 16-19, p. 376

10. Trade-Offs Coal vs. Nuclear Coal Nuclear Ample supply of uranium Ample supply Low net energy yield High net energy yield Low air pollution (mostly from fuel reprocessing) Very high air pollution Low CO2 emissions (mostly from fuel reprocessing) High CO2 emissions High land disruption from surface mining Much lower land disruption from surface mining High land use Moderate land use High cost (even with huge subsidies) Low cost (with huge subsidies) Fig. 16-20, p. 376